The field of the invention is cellular transporter molecules.
In the course of performing their normal physiological functions, many types of cells, including bacterial cells and those in specialized mammalian tissues such as the liver and kidney, transport a variety of organic molecules across their cell membranes. For example, cells in the proximal tubule of the kidney transport glucose, amino acids, and uric acid across their membranes, and work to eliminate various drugs and toxic substances from the body. All of these molecules are transported across the cell membranes by specialized cellular transporters.
Recently, genes encoding several putative transporters have been identified. These molecules include OCT-1 (organic cation transporter; Grundemann et al., Nature 372:549-552, 1994), OCT-2 (Okuda et al., Biochem. Biophys. Res. Comm. 224:500-507, 1996), NLT (novel liver-specific transporter; Simonson et al., J. Cell Sci. 107:1067-1072, 1994), and NKT (novel kidney-specific transporter; Lopez-Nieto et al., J. Biol. Chem. 272:6471-6478, 1997). While the sequences of these transporters are not highly conserved (at the amino acid level, OCT-1 and NLT are only 30% and 35% identical to NKT, respectively), they do exhibit similar transmembrane (TM) domain hydropathy profiles.